A. Field of the Invention
This invention relates to the field of ophthalmic implants, and more particularly to a device for implantation in the eye for treatment of glaucoma.
B. Statement of Related Art
Glaucoma is an eye condition in which intraocular pressure is increased to an abnormal level. The increase in intraocular pressure causes an optical neuropathy to develop, namely death of certain cells in the retina, leading to restriction in the field of view and eventual blindness if left untreated.
A normal eye maintains proper intraocular pressure by means of circulation, within the eye, of a watery fluid known as aqueous humor. Aqueous humor is continuously produced by the ciliary body and passes through the pupil into the anterior chamber of the eye. In a healthy eye, the aqueous humor passes out of the eye through the trabeculum and the Canal of Schlemm. In persons suffering from glaucoma, the aqueous humor excretory pathway becomes blocked, whereby the aqueous humor cannot pass out of the anterior chamber of the eye at an adequate rate. This causes a rise in intraocular pressure, causing the damage to the retina and eventual blindness.
Glaucoma can be controlled in some patients via medications that increase the drainage of the aqueous humor. Where medication is unsuccessful, surgical treatment to provide a pathway for exit of aqueous humor is usually performed. Various surgical procedures have been developed to treat glaucoma and are described in the medical literature. Known surgical treatments have various shortcomings, including possible excessive loss of aqueous humor during the early post-operative period, and blockage of the passageway created during surgery by scarring.
Attempts have been made to improve surgical methods for treating glaucoma, including using opthalmic implants. These implants typically incorporate a drainage tube to provide a pathway for aqueous humor to exit from the anterior chamber of the eye, and various means to secure the implant to the wall of the sclera or surrounding tissue. A number of implants have been proposed in the patent literature. Representative patents include Richter et al., U.S. Pat. No. 5,968,058, Fisher, U.S. Pat. No. 5,558,630, Krupin, U.S. Pat. No. 5,454,796, Haas et al., U.S. Pat. No. 4,402,681, the patents to Baerveldt et al., U.S. Pat. Nos. 5,476,445 and 5,558,629; Molteno, U.S. Pat. No. 4,457,757; L""Esperance, Jr., U.S. Pat. No. 5,300,020, Lippmann, U.S. Pat. No. 5,073,163; Donowitz, et al., U.S. Pat. No. 3,788,327, and Wong, U.S. Pat. No. 4,521,210. The above-listed patents are fully incorporated by reference herein.
Many of the implants proposed in the above patents require relatively invasive surgical procedures to install the implant. See e.g. the Baerveldt and Wong patents. A group of physicians led by Dr. Reay Brown have proposed a T-shaped implant composed of tubing that is used to relieve intraocular pressure, but their method of implanting the device requires rather elaborate and invasive surgical procedures. Richter et al. proposes an implant that is inserted directly through the sclera in a rather less invasive procedure. Similarly, Donowitz et al. describes insertion of the implant through the cornea either directly, or through a prepared tract.
In a first aspect, an eye implant for treating glaucoma is provided. The implant includes a tubular body member, preferably made from a resilient elastomeric material, which forms a conduit having a first end and a second end. Aqueous humor flows through the conduit out of the eye. The conduit defines a longitudinal axis. A plurality of anchor members are integrally formed with the tubular body member. The anchor members, which can take the form of hollow tubes, are pre-stressed or otherwise formed in a manner or made from a suitable shape memory material such that they are biased to have a relaxed position in which they are oriented in a non-aligned position relative to the tubular body member, such as forming a T shape.
Prior to installation of the implant, a bonding material is applied to the anchor members to provide a means for retaining the anchor members together in an aligned condition relative to the tubular body member to facilitate insertion of the anchors through the wall of the sclera. The bonding material is made from a material that either melts or dissolves when the implant is inserted into the eye. Alternatively, the bonding material could be ablated by a laser after installation of the implant. In either case, the anchor members are released from their aligned condition and allowed to relax and orient themselves in their nonaligned position relative to the tubular body member, to thereby secure the implant against the wall of the sclera.
To further promote installation of the implant in a minimally-invasive surgical procedure, a cutting or blade element is formed on at least one of the anchor members, and preferably on all of them, either directly or by molding or bonding the cutting surface to the anchor members. The cutting element promotes ease of insertion of the anchor members (joined together by the bonding material) though the wall of the sclera. The cutting element is also formed of a dissolvable or meltable material, such that the cutting element also melts or dissolves after the implant has been installed in said eye.
In a preferred embodiment, the tubular conduit further includes a pressure-controlled valve. The valve is preferably adjustable after installation of the implant to change the flow characeristics of the conduit. In the illustrated embodiment, the valve comprises a section of the tubular body member, the section connected to the tubular body member by a flexible connecting portion. The section moves relative to the longitudinal axis in response to pressure changes in the conduit to thereby control the flow of aqueous humor through the conduit. The surgeon may ablate the flexible connecting portion with a laser to promote more flow of aqueous humor if greater pressure release is indicated post-operatively.
In another aspect of the invention, a method for manufacturing an eye implant for treating glaucoma is provided. The method comprises the steps of forming a conduit and a plurality of anchor members from a first resilient material, the anchor members formed such that they have a relaxed condition in a non-aligned position relative to the conduit, securing the anchor members together in an aligned condition relative to the conduit with a bonding material, and applying a cutting element to the anchor members. The cutting element is formed of a second material different from the first material, wherein the second material is adapted to dissolve or melt after the implant has been inserted into the eye.
The present inventive implant and method is believed to have a number of advantages over many prior art implants. In particular, it can be implanted in a minimally invasive manner. It avoids requiring precise incisions into the outer membranes of the eye, surgical repair and closure procedures, and associated post-operative complications.